Strong, lightweight textile fibers are of high interest in various applications such as reinforcing materials of polymer composites or materials for flak jackets. Highly electrically conductive fibers can be used as multifunctional fibers that act as electrodes for supercapacitors, sensors, batteries or actuators while serving as mechanical supports. Such characteristics can be expected from porous structures having a large surface area. In this case, however, loss of mechanical strength is inevitable. Thus, the use of fibers made of only composite materials has received attention as an approach to increase the toughness of reinforcing fibers. Polymers including carbon nanotubes (CNTs) produced by wet spinning are known to have higher toughness than other materials, even cobwebs.
Such high toughness is determined by the ability to align the carbon nanotubes (CNTs) in the fiber direction to maximize the interaction between the carbon nanotubes (CNTs) and the polymers. One reason for limited alignment of the carbon nanotubes (CNTs) is that the carbon nanotubes (CNTs) form aggregates by cross-linking during wet spinning despite the use of dispersants such as surfactants.
Improvements of alignment characteristics and toughness through hot or cold drawing after fiber spinning have been reported to date, but little is known about a method for producing a composite fiber with high toughness by simple binding of constituent materials without involving complicated drawing.
Recent studies on graphene flake (GF) composites suggest the possibility of producing fibers with high strength and toughness. Graphene flakes (GFs) are more advantageous as nanofillers for reinforcement than rod-like carbon nanotubes (CNTs) and increase the stiffness and axial tensile strength of fibers. Graphene plates are known to have an uneven wrinkled surface, contributing to an increase in load transfer through interaction with surrounding matrix materials. The planar structure of GFs increases the contact area with matrix materials compared to rod-like carbon nanotubes (CNTs) having a similar length. The 2-dimensional structure of graphene flakes (GFs) is useful because microcracks may be effectively deflected, tilted, or twisted.
However, despite the need to develop composite fibers using graphene and carbon nanotubes with high strength and toughness, effective fiber production methods have not been proposed so far.